NK'UWIN 

'A  'N  ' 


LESSON  FOR  THE  FARM  HOME 

L.  H.  BAILEY,  Director 
COURSE  FOR  THE  FARM  HOME,  MARTHA  VAN  RENSSELAER,  Supervisor 


n.  NO.  31 


ITHACA,  N.  Y. 
JANUARY  i,  1913 


SANITATION  SERIES  No.  2 


HOUSEHOLD  BACTERIOLOGY  * 

MARTHA  VAN  RENSSELAER 

In  the  vegetable  kingdom  there  are  micro-organisms  that  are  the  smallest 
ind  simplest  plants  known.     They  live  in  soil  and  in  water  and  are  found 
>n  the  surface  of  foodstuffs.     Some 
varieties  prey  on  man  and  beast 
id  plant.    They  number  hundreds 
)f  species,  some  of  which   are   of 
it  value  in  nature's  economy 
ind  of  great  benefit  to  man,  while 
)thers  are    sources  of   danger   to 
:he  health  of  man  and  animal. 
Dust  is  a  conveyance  of   such 
dcro-organisms.     In  itself  dust  is 
ictically  harmless,   although   it 
itates    the   mucous   membrane, 
-atches    furniture,    worries    the 
[housekeeper,   and   occupies  space 
iceded    for  something    else.     We 
:annot  get  rid  of  this  old  enemy; 
[there    will    be    dust    as    long    as 
there    are    people     and     furnish- 
ings.     Wind  is  an  agent  for  dis- 
tributing it.     Housekeepers   have 
probably  always  asked  the  ques- 
tion,   "  Where    does  all  the   dust 
Iconic  from?" 


THE    DUST    GARDEN 


Let  us  have  some  dust  gardens 
Ito  study,  and  note  what  will  be 
[produced.  A  garden  presupposes  plant  life. 


FIG.  24. —  Moving  the  dust  and  germs  from 
one  place  to  another 


Every  garden  has  weeds,  as 


*The  author  is  indebted  for  assistance  in  the  preparation  of  this  bulletin  to  Miss  Maria  Elliott, 
Simmons  College;  Dr.  V.  A.  Moore,  Dean  of  the  New  York  State  Veterinary  College;  and  R.  A.  Pearson, 
[formerly  Commissioner  of  Agriculture  for  New  York  State. 

Published  semi-monthly  throughout  the  year  by  the  New  York  State  College  of  Agriculture  at 
Cornell  University.  Entered  as  second-class  matter  October  13,  19x1.  at  the  post  office  at  Ithaca, 
N.  Y..  under  the  Act  of  Congress  of  July  16,  1894. 


305673 


54 


THE  CORNELL  READING-COURSES 


well  as  plants  that  we  do  not  call  weeds  because  they  are  being  fostered. 

In  the  same  way  our 
microscopic  dust-gar- 
den will  have  both  non- 
useful  and  useful  plants. 
In  the  ordinary  garden, 
weeds  that  are  visible 
may  be  destroyed  with 
a  rake  or  a  hoe.  In 
our  dust  garden  are 
plants  that  are  invisible 
to  the  naked  eye,  and 
the  gardens  in  which 
they  grow  may  be  the 
food  on  our  table,  our 
own  bodies,  or  the  dust 
in  our  houses.  These 
countless  invisible  liv- 
ing organisms  affect  us 

_,  although  we  cannot  see 

FIG.  25.—  What  grew  tn  a  dust  garden 

them.     We  ascribe  the 

products  of  their  activities  to  various  causes.  They  are  active  and 
powerful  in  bringing 
about  certain  amazing 
transformations  in  mat- 
ter, but  we  need  more 
than  the  lens  of  the 
human  eye  to  detect 
them.  Since  either 
good  or  harm  may 
result  from  the  presence 
of  these  invisible  liv- 
ing individuals,  we  find 
that  it  is  as  desirable 
to  cultivate  some  as  to 
exclude  others. 

Glass  boxes,  fitted 
loosely  with  glass  covers 
through  which  much 
that  takes  place  inside 
may  be  seen,  are  shown  FlG'  26'~  Another  dust  zarden 

in  Figs.  25  and  26.    One  day  these  glass  boxes  served  as   garden  beds. 


SUPPLEMENT  TO 


LESSON  FOR  THE  FARM  HOME 

L.  H.  BAILEY,  Director 
COURSE  FOR  THE  FARM  HOME,  MARTHA  VAN  RENSSELAER,  Supervisor 


VOL.  II.  No.  31  JA™  A*Y  ?' Jl3  SANITATION  SERIES  No.  a 

HOUSEHOLD  BACTERIOLOGY 

DISCUSSION    PAPER 

This  discussion  paper,  accompanying  the  lesson  on  Household  Bac- 
teriology, may  be  returned  with  answers  to  the  questions  and  with  any 
suggestions  and  questions  of  your  own.  While  the  answering  of  these 
questions  is  not  absolutely  necessary,  a  much  greater  benefit  will  be 
derived  if  you  give  to  others  the  benefit  of  your  own  experience.  It  will 
also  help  us  to  understand  your  point  of  view.  The  lesson  may  be  used 
in  the  grange  and  in  the  club  where  these  subjects  are  considered. 

i.  The  exposure  to  dust,  in  open  store-windows  and  in  wagons,  of  fruit 
and  vegetables  to  be  used  later  on  the  table  is  dangerous  because  the  pro- 
ducts collect  on  their  surfaces  germs  that  may  be  communicated  to  the 
consumer.  Would  it  not  encourage  care  on  the  part  of  the  seller  if  house- 
wives objected  to  purchasing  such  provisions?  Discuss. 


Published  semi-monthly  throughout  the  year  by  the  New  York  State  College  of  Agriculture  at  Cornell 
University.  Entered  as  second-class  matter  October  13,  1911,  at  the  post  office  at  Ithaca,  N.  Y.,  under 
the  Act  of  Congress  of  July  16,  1894. 


2.  How  much  does  the  effort  to  make  clean,  wholesome  surroundings 
really  add  to  the  amount  of  work  in  the  house? 


3.  What  do  you  consider  the  most  important  ways  in  which  you  can 
apply  the  knowledge  gained  from  the  study  of  household  bacteriology? 


Name. . 
Address 
Date..  . .-. . 


HOUSEHOLD  BACTERIOLOGY  55 

The  soil  used  was  a  kind  of  beef-broth  jelly.  The  seed  was  ordinary 
dust  from  an  ordinary  room.  The  boxes  had  been  baked  for  over  an 
hour  in  a  very  hot  oven.  The  jelly  had  been  steamed  a  number  of  times, 
until  no  living  thing  could  possibly  be  therein. 

A  dust  garden  planted  after  a  room  had  been  carefully  swept  is  shown 
in  Fig.  25.  When  the  cover  of  the  box  was  removed  and  the  dust  raised 
by  the  broom  into  the  air  had  settled  on  the  soft,  sticky  jelly,  something 
happened!  In  about  twenty-four  hours  little  specks  appeared,  which 
rapidly  or  slowly  grew  larger  and  developed  various  colors.  Unfortunately, 
the  photograph  does  not  show  the  delicate  greens,  yellows,  and  blues  of 
the  different  spots.  As  they  grew  larger  some  spots  revealed  a  feathery 
or  velvety  surface  and,  like  that  at  the  left  side,  a  dark  center  with  dust 
flying  from  it.  The  other  spots  were  shiny,  wet,  or  waxy  in  appearance, 
and  never  showed  any  increase  in  height  or  any  dark,  dusty  center. 

Every  housewife  who  has  seen  mold  on  her  bread  or  on  her  jelly,  in 
her  pickle  jar,  or  possibly  on  shoes  and  books,  will  suspect  that  the  velvety, 
dark-centered  spots  are  of  similar  nature.  Molds  spread  their  cells  over 
the  food,  sending  some  cells  down  into  the  substance  and  others  upward. 
From  the  tops  of  the  upright  cells  grow  others,  and  in  or  on  them  are  formed 
thousands  of  dust-like  specks,  called  spores.  Each  of  these  spores  may 
start  a  new  bed  of  mold.  The  infinitely  tiny  spores  falling  on  soft  sub- 
stances, such  as  cheese  or  bread,  send  invisible  lacy  threads  down  into 
the  substances;  while  on  books,  leather,  wood,  or  cloth  they  may  grow 
only  over  the  surface  and  may  remain  invisible. 

Certain  spots  in  the  dust  garden  are  colonies  of  bacteria.  Each 
spot  shows  where  one  plant  or  cell  touched  the  jelly.  This  cell  fed,  and 
divided  itself  in  the  middle.  These  two  cells  repeated  the  process,  until 
perhaps  there  were  a  hundred  or  more.  Then  a  tiny  speck  became  visible. 
No  one  ever  saw,  with  the  naked  eye,  a  single  bacterium  or  a  mold  spore. 

In  Fig.  26  is  shown  a  dust  garden  with  soil  exactly  like  that  of  the  one 
shown  in  Fig.  25,  but  the  dust  that  planted  it  was  thrown  into  the  air 

by  using  a  feather  duster. 

' 

KINDS    OF    PLANT    MICRO-ORGANISMS 

Dust  plants  are  micro-organisms.  There  are  large  numbers  of  minute 
organisms  so  small  that  they  cannot  be  seen  by  the  naked  eye  but  require 
the  aid  of  a  powerful  microscope  to  show  their  presence;  hence  their 
name,  "  micro-organisms."  Various  names  have  been  given  to  these 
minute  living  bodies,  such  as  "  germs  "  and  "  microbes."  Literally, 
germ  means  the  beginning,  the  first  living  cell  that  produces  a  more  com- 
plex form. 

The  plant  micro-organisms  that  we  shall  consider  are  bacteria,  molds, 
and  yeasts. 


56  THE  CORNELL  READING-COURSES 

Bacteria 

Bacteria  are  carried  on  particles  of  dust,  in  liquids,  and  on  the  surface 
of  fruits  and  vegetables  as  well  as  other  articles  of  food  exposed  in  the 
market.  They  may  possibly  find  their  way  into  the  house  by  means 
of  drains,  and  they  are  carried  by  insects.  Normally,  they  are  found 
in  the  air,  in  the  soil,  in  water,  in  food,  in  the  mouth  and  the  digestive 
tract,  on  the  skin,  under  the  nails,  in  the  hair,  in  the  clothing. 

Bacteria  are  reproduced  by  a  process  of  division  known  as  "  fission," 
some  of  the  different  forms  of  which  are  shown  in  Fig.  27.  The  rapidity 
of  reproduction  depends  on  warmth,  moisture,  and  food  supply.  Some 
species  produce  a  new  generation  every  half-hour;  thus  a  single  bacterium, 
if  its  growth  were  totally  unchecked,  might  become  in  twelve  hours  an 
ancestor  of  sixteen  million  descendants.  In  two  days  the  descendants 


•  ''•' 


FIG.  27.  —  Various  forms  of  bacteria,    or    germs,    showing    different 
methods  of  fission.     Greatly  magnified 

would  fill  a  pint  measure.  This  rapidity  of  reproduction  does  not  occur, 
because  there  are  countless  checks  to  the  life  of  every  species  of  bacteria. 
We  may  form  some  idea  of  the  minuteness  of  bacteria  when  we  con- 
sider that  the  length  of  a  single  bacterium  of  some  species  is  1/25,000  of 
an  inch.  Many  thousands  of  them  may  be  packed  into  the  space  that  a 
grain  of  sugar  would  occupy.  If  one  falls  into  a  minute  wrinkle  of  the 
hand,  it  is  as  though  it  had  fallen  into  a  deep  ditch. 

Molds 

Molds  also  are  micro-organisms.  A  colony  of  mold  organisms  growing 
on  some  substance  forms  a  velvety  pile  having  a  dark  center.  We  often 
see  long  threads  budding  and  branching  to  form  a  network  over  food. 
Each  head  produces  thousands  of  dust-like  spores.  Some  molds  grow 
with  less  moisture  than  is  required  for  bacteria,  and  some  flourish  in  the 
light.  They  are  frequently  found  in  bread,  on  meat,  on  leather,  and  on 
sugary  liquids.  They  increase  very  rapidly  after  rainstorms,  and  wind 
affects  them  less  than  it  does  bacteria. 


HOUSEHOLD  BACTERIOLOGY  57 

Mildew  is  a  form  of  mold  found  on 'moist  clothes  that  have  not  been 
exposed  to  the  fresh  air.  Mustiness  is  an  indication  of  mold.  Ringworm 
is  due  to  this  species  of  organism,  which  gets  under  the  skin  and  causes 
inflammation. 

Yeasts 

The  illustrations  do  not  show  a  third  kind  of  plant  micro-organism 
which,  especially  in  the  country,  is  often  present  in  house  dust.  That 
organism  is  yeast,  which  also  is  a  single  cell  but  which  is  reproduced  by 
little  buds  that  swell  out  from  the  parent  cell  and  may  or  may  not  break 
off  later.  Those  that  float  freely  in  the  air,  both  inside  and  outside  the 
house,  are  called  "  wild  yeasts."  So  far  as  shape,  size,  and  method  of 
reproduction  are  concerned,  these  are  little  different  from  the  cultivated 
yeast  plants  used  to  raise  bread  or  to  give  the  "  sparkle  "  to  sweet  fer- 
mented liquids,  such  as  beer. 

As  the  invisible  yeast  plants  can  remain  alive  for  a  long  time  without 
moisture,  we  may  have  them  furnished  to  us  in  dried  cakes  as  well  as 
in  the  fresh  compressed  form. 

To-day,  even  with  the  cultivated  yeasts,  the  housewife  who  mixes 
her  sponge  in  a  dusty  room,  in  dusty  utensils,  with  old  yeast  —  or  with 
everything  clean  and  fresh,  if  she  lets  the  sponge  rise  too  long  or  keeps 
it  too  hot  —  is  likely  to  have  sour  bread.  Bacteria  can  grow  well  when 
and  where  yeast  cannot,  so  that  acid  will  be  made  from  the  alcohol  that 
the  yeast  makes  from  sugar.  The  yeast  plants  grow  best  at  a  medium 
temperature,  about  75°  to  90°  F.,  which  is  an  average  "  summer  heat." 
In  a  temperature  above  90°  F.  yeast  cannot  grow  so  well,  but  bacteria 
grow  better. 

The  little  yeast  plant,  although  so  small  and  simple  in  structure,  is 
endowed  with  many  of  the  powers  of  trees  and  vegetables  and  other 
higher  plants.  It  requires  food,  has  a  certain  range  of  temperature  in 
which  it  grows  best,  and  is  injured  or  killed  by  too  high  or  too  low  tem- 
perature or  by  too  little  moisture.  If  it  be  given  favorable  conditions  it 
will  .feed,  grow  rapidly,  and  reproduce  itself  by  swelling  out  one  part 
into  a  bud,  which  may  or  may  not  break  away  from  the  mother  cell.  The 
most  favorable  temperature  for  the  rapid  growth  of  the  yeast  plant,  as 
already  stated,  is  75°  to  90°  F.  Below  that  temperature  the  plant  will 
not  grow  rapidly  and  therefore  cannot  do  much  work;  at  a  temperature 
much  above  90°  it  will  be  killed,  and  a  dead  plant  cannot  work  any  more 
than  a  dead  animal  can. 

The  work  of  the  yeast  plants  is  to  change  the  sugar  in  bread  sponge  into 
two  substances  —  alcohol,  and  a  gas  called  carbon  dioxid.  The  millions 
of  little  bubbles  in  the  sponge  cannot  break  through  the  sticky  gluten 


5 8  THE  CORNELL  READING-COURSES 

of  the  flour,  so  they  raise  the  whole  mass.  When  the  bread  is  baked  the 
gas  is  dissipated,  the  gluten  walls  of  these  bubbles  are  hardened,  and 
little  holes  remain,  filled  with  air  only.  The  alcohol,  too,  is  driven  off 
by  the  heat. 

It  is  very  difficult  to  keep  weeds  out  of  the  vegetable  garden  because 
their  seeds  are  carried  to  the  soil  in  many  ways.  When  the  weeds  have 
sprouted  or  grown  a  little,  they  may  be  pulled  up  easily.  In  the  bread- 
garden  we  want  only  yeast  to  grow,  but  it  is  very  difficult  to  insure  its 
growth  alone  since  in  the  bread  garden  neither  the  good  plants  nor  the 
weeds  ever  become  visible.  In  no  other  way  does  household  bacteriology 
interest  the  housekeeper  so  much  as  when  connected  with  the  baking 
of  her  bread. 

Compressed  yeast-cakes  and  dry  yeast-cakes  consist  of  a  mass  of  yeast 
plants  mixed  with  some  form  of  starch  and  pressed  into  cakes.  One  yeast- 
cake  may  contain  one  half -billion  yeast  plants.  It  should  contain  only 
one  species  of  yeast,  but  oftentimes  other  plants  gain  access  to  the  mixture. 
If  a  compressed  yeast-cake  has  been  kept  over  a  day  or  two  it  begins 
to  turn  dark  and  to  soften.  That  is  an  indication  that  the  yeast  plants 
are  dying  and  that  bacteria  have  gained  access  to  the  cake,  thus  causing 
decay.  The  cake  should  then  be  discarded,  for  it  will  not  make  good 
bread.  If  dough  is  left  too  long  or  if  it  is  kept  too  warm,  the  yeast  plants 
become  weakened;  then  the  bacteria  that  may  be  present  grow  and  pro- 
duce an  acid,  making  the  bread  sour.  We  scald  the  milk  used  in  making 
bread  in  order  to  destroy  the  bacteria  present.  We  bake  bread  for  a  full 
hour,  or  longer  if  the  loaf  is  very  large,  in  order  to  kill  bacteria,  yeasts, 
and  molds,  as  all  three  may  be  present  in  a  poorly  baked  loaf  of  bread 
and  interfere  not  only  with  the  keeping  quality  of  the  bread,  but  also 
with  the  health  of  the  consumer.  The  careful  housekeeper  will  have 
clean  dishes  in  which  to  measure  her  ingredients  and  to  mix  her  bread. 
She  will  not  sweep  nor  cause  a  dust  to  rise  in  the  room  where  she  makes 
her  bread,  because  bacteria  are  in  that  way  raised  into  the  air  and  may 
settle  on  her  dough.  She  will  cover  the  dough  in  order  to  keep  out 
dust.  With  all  her  care  there  will  always  be  some  bacteria  present,  but 
they  do  not  thrive  in  the  sugar  solution  so  well  as  healthy  yeast  plants 
do  and  at  the  temperature  used  for  bread-making  they  do  not  grow  so 
rapidly  as  do  the  yeast  plants.  They  like  the  alcohol  that  the  yeast 
makes  from  the  sugar,  however,  so  dough  is  kept  at  summer  heat  only 
long  enough  for  the  yeast  to  produce  sufficient  gas  to  raise  the  bread  but 
not  long  enough  for  bacteria  to  get  a  start.  It  is  better  not  to  wrap 
cloth  around  hot  bread  just  taken  from  the  oven,  because  moisture  and 
warmth  favor  the  growth  of  bacteria  and  bread  that  is  cooled  slowly  may 
not  keep  so  well  as  if  cooled  more  rapidly. 


HOUSEHOLD  BACTERIOLOGY  59 

GERMS  THAT  ARE  NOT  HARMFUL 

Some  bacteria  are  of  great  value  in  the  economy  of  nature.  Man's 
bacterial  friends  have  been  found  not  less  active  than,  and  many  times 
as  numerous  as,  his  bacterial  foes.  To  his  bacterial  friends  he  owes  the 
fertility  of  the  soil  by  which  plants  are  nourished.  They  tear  down 
organic  matter  and  pass  it  back  to  its  simpler  elements  through  the  process 
of  decay,  thus  ridding  the  earth  of  many  harmful  substances.  This  is 
the  work  of  so-called  nature's  scavengers.  There  is  advantage  in  what 
is  called  incipient  decay.  When  bacteria  grow  in  food  the  products  of 
decomposition  are  different  from  the  original  nature  of  the  food  and 
produce  new  odors  and  tastes.  We  often  need  the  flavors  thus  produced 
to  stimulate  the  flow  of  the  digestive  juices.  The  gamy  taste  of  meat  is 
due  to  the  beginning  of  decomposition  of  some  of  its  constituents,  and 
the  strong  flavor  of  limburger  cheese  is  owing  to  the  same  cause.  Gamy 
food,  however,  soon  becomes  objectionable;  and  cheese  is  ruined  by  the 
development  of  a  too  strong  flavor  of  putrefaction. 

The  most  common  substances  that  owe  their  flavor  largely  to  the 
presence  of  bacteria  are  butter,  cheese,  and  vinegar.  Without  bacteria, 
butter,  like  "  apple-pie  without  the  cheese,"  lacks  flavor;  while  cheese 
without  bacteria  would  be  like  "  the  play  '  Hamlet '  with  Hamlet  left 
out  "  —  an  utter  impossibility.  When  you  next  enjoy  the  acidity  of 
a  pickle,  remember  to  give  credit  for  that  pleasant  sourness  to  certain 
tiny  plants,  such  as  those  that  you  have  seen  massed  together  in  enormous 
quantities  in  "  mother  "  of  vinegar.-  Whenever  a  liquid  containing  a 
small  amount  of  alcohol  cider,  for  example,  is  exposed  to  the  air,  bacteria 
find  therein  a  home  and  food.  A  film  similar  in  nature  to  "  mother  " 
spreads  over  the  top  of  the  liquid  and  before  long  the  alcohol  becomes 
acetic  acid,  with  vinegar  as  the  result. 

Our  Puritan  grandmothers  would  have  thought  us  bewitched  had  we 
been  able  to  tell  them  that  their  cheeses,  on  which  they  spent  so  many 
watchful  hours,  owed  their  making  and  their  flavor  largely  to  invisible 
plaints.  Even  now  scientists  are  unable  to  explain  this  process  fully, 
although  they  are  certain  that  there  could  be  no  cheese  without  bacteria. 

From  none  of  the  harmless  bacteria  do  we  get  more  real  enjoyment 
than  from  those  found  in  butter.  Long  before  the  science  of  bacteriology 
and  the  days  of  cream  separators,  it  was  known  that  cream  set  to  rise 
by  its  own  lightness,  skimmed,  and  left  standing  for  several  days  would 
"  ripen  "  and  make  far  better  butter  than  fresh  cream.  Butter  made 
from  ripened  cream  was  found  to  taste  better,  keep  better,  and  be  made 
more  easily  than  that  made  from  unripened  cream.  We  needed  the 
bacteriologist  to  find  the  cause  and  to  prove  it  to  be  the  presence  of  bac- 
teria; but  long  before  his  day  the  thrifty  housewife  had  made  use  of  the 


60  THE  CORNELL  READING-COURSES 

principle  involved,  and  had  unknowingly  availed  herself  of  the  assistance 
of  the  invisible  plants. 

The  action  of  bacteria  is  very  useful  in  the  production  of  linen,  jute, 
and  hemp,  in  the  tanning  of  leather,  and  in  the  maceration  of  skeletons. 
The  destruction  of  garbage  by  means  of  the  septic  tank  is  owing  to  a  certain 
class  of  bacteria. 

METHODS  OF  DESTROYING  THE  EFFECTS  OF  BACTERIA 

Heat 

All  bacteria  are  promptly  killed  by  heat  unless  they  are  in  the  spore 
form  or  the  resting  stage.  There  are  resting  stages  of  some  of  these 
organisms  when  the  conditions  for  active  life  are  unfavorable.  The 
organism  itself  may  dry  up  and  assume  a  dormant  form,  resuming  its 
active  form  when  favorable  conditions  recur;  or  it  may  throw  off  spores. 
Spores  resist  heat  far  better  than  does  the  active  or  vegetative  organism ; 
so,  although  we  may  have  used  enough  heat  to  kill  the  active  forms,  we 
cannot  be  sure  that  we  have  destroyed  all  organisms  unless  we  know  that 
the  particular  organism  which  we  seek  to  exterminate  does  not  form  spores 
or  is  not  in  the  spore  stage.  Boiling  for  twenty  minutes  will  generally, 
but  not  always,  kill  most  forms  of  bacteria,  including  the  spores.  Water 
is  pronounced  safe  when  it  is  thus  boiled.  Mere  simmering  of  water  is 
not  sufficient. 

Fresh  air  and  sunshine 

Direct  sunshine  kills  most  bacteria.  Many  persons  are  afraid  to  take 
fresh  air  and  sunshine  in  sufficient  quantities  to  counteract  the  bad 
influence  of  dark  rooms,  moisture,  and  poor  air;  yet,  of  all  the  bactericides 
known  there  is  none  that  compares  in  effectiveness  with  sunshine.  Much 
suffering  would  be  saved  if  persons  could  only  be  brought  to  a  realization 
of  this  fact.  Airing  and  ventilating  bedrooms,  kitchens,  cellars,  and 
stables  aids  much  in  keeping  them  wholesome. 

Drying 

About  thirty  per  cent  moisture  is  required  for  the  growth  of  bacteria. 
This  fact  is  the  principle  utilized  in  the  preservation  of  many  of  our  foods. 
In  order  to  preserve  seeds  we  dry  them,  and  they  do  not  begin  to  sprout 
until  they  are  moistened  when  needed  for  planting.  Flour  is  practically 
free  from  decomposition  because  it  is  dry,  and  a  cracker  keeps  indefinitely 
for  the  same  reason.  In  some  regions,  tons  of  fish  are  prepared  for  market 
by  drying.  Fruits,  such  as  berries,  raisins,  apricots,  currants,  prunes,  and 
apples,  are  preserved  in  this  way.  Dried  beef  has  long  been  a  familiar 
example  of  the  application  of  this  principle.  It  must  be  remembered 


HOUSEHOLD  BACTERIOLOGY  61 

that  drying  only  arrests  the  growth  of  bacteria,  and  that  when  food  has 
over  30  per  cent  of  moisture  there  is  danger  of  its  spoiling.  Dried 
foods  are  therefore  kept  in  a  dry  place  so  as  to  prevent  absorption  of 
moisture  and  consequent  spoiling. 

Cold-storage 

As  a  means  of  preventing  putrefaction  and  decay,  storehouses  are 
cooled  artificially  and  a  low  and  constant  temperature  is  maintained. 
Eggs,  fruit,  vegetables,  and  the  like  may  be  kept  for  a  considerable  period 
of  time  if  they  are  frozen,  and  may  then  be  delivered  at  the  market  in  fair 
condition  for  use.  There  is  some  question,  however,  regarding  the  safety 
of  the  use  of  cold-storage  foods,  for  food  deteriorates  quickly  if  it  is  taken 
from  cold-storage  and  not  used  immediately  thereafter.  As  long  as  meats 
are  kept  frozen  they  may  be  preserved  indefinitely.  Ordinary  ice-chests 
are  very  efficient  for  arresting  the  growth  of  bacteria,  although  the  tem- 
perature in  them  is  higher  and  less  uniform  than  in  cold-storage  and  they 
cannot  be  depended  on  for  keeping  foods  for  any  length  of  time.  Bac- 
teria grow  very  slowly,  however,  in  an  ice-chest.  The  same  statement 
is  true  regarding  certain  materials  that  have  antiseptic  power  in  a  cool 
cellar. 

Preservatives 

Antiseptics  are  materials  that  retard  or  prevent  the  growth  of  bacteria. 
They  may  be  used  for  the  preservation  of  foods,  but  they  should  be  harm- 
less to  man.  Substances  often  used  as  preservatives  are  borax,  boracic 
acid,  salicylic  acid,  and  formalin.  In  small  quantities  these  preservatives 
have  not  been  found  to  be  very  injurious;  yet  their  use  in  manufactured 
foods  has  been  made  illegal  in  many  States,  as  their  presence  in  food 
might  quickly  lead  to  the  consumption  of  amounts  sufficient  to  be  harm- 
ful. The  housekeeper  never  knows  how  much  preservative  may  have 
been  used  before  articles  of  food  come  to  her,  hence  it  is  safe  for  her  never 
to  use  any  preservative  but  to  depend  instead  on  the  bactericidal  action 
of  heat.  It  is  not  known  how  much  the  digestive  organs  can  endure 
from  borax  and  similar  materials,  but  experiments  seem  to  show  that  such 
materials  have  a  detrimental  influence. 

Harmless  preservatives. —  (a)  Sugar.  A  heavy  sugar  solution  prevents 
the  growth  of  bacteria.  In  the  proportion  of  40  or  50  per  cent,  sugar 
makes  an  excellent  preservative  and  is  commonly  used  in  this  amount  in 
the  preparation  of  jellies,  marmalades,  and  preserves  and  in  preserving 
raisins,  figs,  and  candied  fruits.  Condensed  milk  is  also  preserved  by 
the  addition  of  30  or  40  per  cent  of  sugar. 

(b)  Salt  is  very  commonly  used  in  the  household  to  prevent  bacterial 
growth.  The  housekeeper  uses  it  for  keeping  fat  pork,  for  corning  beef  and 


62  THE  CORNELL  READING-COURSES 

bacon,  for  preserving  eggs,  hams,  fish,  and  the  like.  Butter  and  cheese 
are  salted  partly  for  flavor,  but  largely  for  the  sake  of  making  them  keep 
better. 

(c)  Acids  protect  food  from  bacteria  and  give  a  new  flavor  that  many 
find  acceptable.     In  making  pickles  we  soak  cucumbers  in  brine  and  add 
vinegar   and    spices   to   preserve   them.     The   brine  sometimes  becomes 
covered  with  a  scum,  owing  to  bacterial  growth,  and  the  pickles  grow 
soft  through  decay;  these  facts  show  that  salt  by  itself  is  not  a  perfect 
preservative.     The  remedy  in  the  case  of  the  pickles  is  to  scald  them,  in 
order  to  destroy  micro-organisms.     Other  acids  are  known  to  preserve 
foods.      This  is   the   case    with    sauerkraut,    which  is    protected    from 
bacterial  growth  not  only  by  acetic  acid  but  also  by  lactic  acid,  produced 
by  allowing  bacteria  to  grow  in  the   sauerkraut.     The   resulting   acid 
finally  destroys  the  organisms  that  have  produced  it,  and  aids  in  pre- 
venting the  entrance  of  others. 

(d)  Spices  are  antiseptic  and  are  added  to  foods  in  order  to  prevent 
putrefaction.     Mincemeat  is  a  good  illustration  of  this  practice.     The 
apples  and  meat  would  putrefy  very  quickly  were  it  not  for  the  spices 
and  boiled  cider  that  are  added  to  prevent  putrefaction.     We  add  sage 
and  spices  to  sausage  for  the  same  purpose,  while  fruit  cake  is  kept  for 
a  long  time  by  the  same  means.     Hops  not  only  give  a  nutty  flavor  to 
bread  and  food  in  which  they  are  used,  but  also  have  a  slightly  antiseptic 
action. 

Canning 

Canning  keeps  fruit  and  vegetables  free  from  all  bacterial  growth 
because  it  first  destroys  all  life  present  and  then  provides  for  complete 
exclusion  of  further  organisms.  As  bacteria  are  found  on  utensils,  in 
the  air,  and  in  water,  and  all  food  materials  contain  them,  we  first  destroy 
the  bacteria  by  boiling  the  food,  and  then  seal  the  can,  which  has  been 
thoroughly  sterilized,  in  order  to  prevent  the  entrance  of  bacteria. 
The  housekeeper  has  learned  that  a  single  bacterium  in  a  can  is  sufficient 
to  destroy  the  entire  contents.  Formerly  she  might  have  said,  "  I  do 
not  lose  many  cans  of  fruit  in  a  year."  With  her  present  knowledge  of 
the  necessity  for  complete  sterilization  she  may  say,  "  I  never  lose  a  can 
of  fruit." 

This  statement  is  made  possible  only  by  thorough  sterilization  and  her- 
metic sealing  of  the  receptacles  used  in  canning.  Some  articles  of  food 
have  to  be  cooked  for  a  long  time  before  becoming  completely  sterilized, 
because  they  contain  spores  that  may  resist  ordinary  boiling.  Most 
failures  in  canning  are  owing  to  the  use  of  insufficient  heat  or  to  failure  to 
sterilize  all  the  utensils  used,  thus  leaving  spores,  which,  developing  later, 
will  spoil  the  material  canned.  Spores  get  in  accidentally.  It  is  necessary 


HOUSEHOLD  BACTERIOLOGY  63 

to  prevent  the  raising  of  dust  and  to  avoid  the  use  of  cloths  or  utensils 
not  thoroughly  cleansed.  Persons  will  give  themselves  much  concern 
in  sterilizing  fruit  and  jars,  and  then  wipe  out  the  clean  jar  with  a 
dishcloth  or  let  their  fingers  come  in  contact  with  the  inside  of  the  jar. 
Everything  that  comes  in  contact  with  fruit  or  receptacle  should  not 
only  be  clean  but  should  also  be  sterile. 

Cans  must  be  sealed  while  still  hot,  so  as  to  sterilize  any  air  present. 
New  rubber  rings  should  be  used  each  year,  as  they  need  to  be  soft  and 
elastic,  and  they  should  be  heated  in  water  before  being  used.  Sterili- 
zation can  be  accomplished  much  more  thoroughly  in  factories  than  in 
private  houses,  because  the  former  have  equipment  to  produce  sterilization 
under  pressure.  Never  is  the  housekeeper  more  conscious  of  the  necessity 
of  exact  laboratory  principles  than  when  she  is  canning  her  fruit;  it  is  a 
piece  of  work  of  which  to  be  proud,  when  she  does  it  with  the  exact- 
ness of  scientific  principles. 

DISEASE   GERMS 

A  growing  knowledge  of  bacteria  has  done  much  toward  preserving  or 
prolonging  life.  Some  persons  still  state  that  they  are  happier  if  they  do 
not  know  too  much  about  germs.  They  affirm  that  before  germs  were 
known  people  were  just  as  healthy  as,  and  much  happier  in  their  ignorance 
than,  at  the  present  time.  They  confound  knowledge  with  fear.  Knowledge 
teaches  prevention;  fear  preys  on  the  mind.  A  lack  of  knowledge  of  how 
to  avoid  infection  is  inexcusable  among  the  intelligent.  An  infected 
person  should  be  isolated  for  the  welfare  of  his  fellow-beings,  even  though 
he  is  suffering  merely  from  a  cold.  Every  one  now  understands  that  a 
cold  is  contagious.  With  isolation  to  prevent  others  from  becoming 
infected,  and  disinfection  to  kill  already  existent  germs,  sickness  and  the 
death  rate  would  be  soon  and  greatly  reduced.  A  student  who  was 
interested  in  his  work  had  mumps.  He  was  asked  by  his  instructor  to 
remain  away  from  class  until  he  was  well.  On  his  refusing  to  do  so,  the 
dean  Q£  the  college  told  him  that  he  must  leave  the  college  until  he  was 
pronounced  safe.  The  student  said  that  he  could  not  understand  why 
he  should  not  remain  in  the  college  because  it  was  his  mumps.  The 
truth  is  that  he  could  not  keep  his  mumps  to  himself. 

Some  micro-organisms  are  parasites  that  produce  disease.  They  feed 
on  living  plants  and  animals.  Other  micro-organisms  live  on  both  living 
and  dead  material.  They  are  only  partly  parasitic  and  are  capable  of 
producing  disease.  Those  microbes  that  cause  disease  are  said  to  be 
"  pathogenic."  It  is  now  known  that  microbes  are  the  cause  of  many  of 
the  contagious  or  infectious  diseases,  such  as  tuberculosis,  diphtheria,  and 
typhoid  fever.  The  better  the  conditions  for  the  propagation  of  these 


64  THE  CORNELL  READING-COURSES 

injurious  germs  if  they  should  gain  entrance,  the  greater  is  the  danger  ot 
disease. 

There  is  reason  to  hope  that  at  no  very  distant  day  the  spread  of  infec- 
tious diseases  may  be  controlled,  since  it  is  generally  known  that  there 
are  specific  living  disease  germs  that  pass  from  a  patient  to  another  person. 
If  a  person  becomes  infected  with  disease  germs  it  is  quite  possible  for 
him  to  pass  on  these  germs  to  others  through  careless  habits.  Cases  of 
sickness  cared  for  at  home  —  and  this  covers  a  large  percentage  of  cases  — 
make  it  necessary  for  the  housekeeper  to  safeguard  members  of  her  family, 
as  well  as  other  persons,  by  a  knowledge  of  bacteriology  and  a  strenuous 
care  to  prevent  infection.  In  the  hospital  such  safeguarding  is  much  more 
easily  managed.  Hospital  methods,  however,  may  extend  to  the  home. 

PRACTICAL   APPLICATION    OF    PRINCIPLES    OF    BACTERIOLOGY 

Thoughtfulness,  together  with  a  knowledge  of  the  results  of  bad  habits, 
brings  many  things  to  our  notice  to  which  we  may  have  previously  closed 
our  eyes.  We  are  prone  to  object  to  dirt  without  stopping  to  consider 
whether  it  is  harmful  dirt.  Our  housekeeping  sensitiveness  worries  us 
if  a  neighbor  calls  and  sees  dust  on  the  table.  This  dust  may  be  less 
harmful,  however,  than  a  spoon  dipped  into  the  food  that  the  cook  is  pre- 
paring for  a  meal,  and  then  placed  again  in  the  food  without  being  washed. 
Kissing. —  Kissing  is  a  custom  as  old,  probably,  as  the  history  of  human 
beings,  and  no  doubt  to  be  continued  but  to  be  indulged  in  only  when 
persons  are  in  a  healthy  condition.  Mothers  are  able  to  control  the 
custom  of  kissing  babies  for  a  short  period;  they  may  lay  a  ban  on  the 
kissing  of  their  infants  by  the  admiring  public.  They  should  even  control 
their  own  desire  to  kiss  their  children  when  affected  with  tuberculosis  or 
suffering  from  tonsilitis  or  other  inflammatory  condition  of  the  mouth  or 
throat. 

"  If  a  body  meet  a  body 

Coming  through  the  rye, 
Can't  a  body  kiss  a  body 
For  fear  of  bacilli?" 

Care  of  finger  nails. —  We  may  wash  our  hands  thoroughly,  but  under- 
neath the  nails  may  be  dirt,  difficult  to  reach,  which  is  a  retreat  for  germs. 
Clean  finger  nails  are  always  an  asset,  but  in  the  handling  of  food  they 
are  essential  to  safety. 

Coughing  and  sneezing. —  For  coughing  and  sneezing  "in  the  open" 
there  is  no  excuse.  A  handkerchief  should  be  within  easy  reach  to  catch 
the  offending  spray  from  the  mouth  and  nostrils.  The  truth  of  this  state- 
ment is  an  argument  for  a  pocket  in  a  woman's  dress,  in  which  to  keep  the 
handkerchief. 


HOUSEHOLD  BACTERIOLOGY  65 

Handling  of  toilet  articles. —  The  fingers  of  the  attendant  may  after  such 
handling  unconsciously  carry  to  the  mouth  infecting  organisms. 

Care  of  discharges. —  Body  discharges  contain  the  seed,  or  germ,  of 
disease.  These  should  not  be  left  carelessly,  as  in  the  case  of  sputum,  to 
dry  and  be  wafted  about  by  the  wind,  nor  thrown  in  a  loose  vault  and 
allowed  to  reach  the  well  or  a  body  of  water  from  which  drinking  water 
is  obtained. 

Insect  pests. — The  fly  is  no  longer  unpopular  merely  because  of  tradition  and 
because  of  its  annoying  bites  and  specks,  but  also  because  of  the  now  well- 
known  fact  thati  it  carries  disease  germs  on  its  feet  and  in  its  body.  Mosqui- 
toes, too,,  are  in  disgrace,  for  without  them  malaria  would  trouble  no  one. 


Common  drinking  glass  Recently  washed  glass 

FIG.  28. —  Public  drinking  cups 

BY  COURTESY  OF  MEDICAL  REVIEW  OF  REVIEWS 

Other  animal  disturbers. —  Rats  harbor  the  flea  that  spreads  the  germ 
of  the  Jsubonic  plague.  Cats  and  dogs  are  the  delight  of  children  and  of 
many  grown  folks,  nevertheless  they  sometimes  bring  with  them  germs 
of  diphtheria,  scarlet  fever,  and  other  diseases. 

The  common  comb  and  brush. —  Common  toilet  articles,  unless  thor- 
oughly sterilized,  are  to  be  avoided  in  the  barber  shop,  shampoo  parlors, 
and  even  in  the  family,  because  dandruff  and  some  other  skin  diseases  are 
infectious. 

The  common  cough-medicine  bottle. —  The  medicine  bottle  may  contain 
not  only  an  opiate  to  paralyze  the  nerves,  but  also  a  cold-germ  from  the 
lips  of  the  last  patient  who  has  placed  the  bottle  to  his  lips. 

The  common  drinking-cup. —  Public  sentiment  has  dealt  a  blow  to  the 
common  drinking-cup.  We  never  think  in  our  homes  of  using  the  same 


66  THE  CORNELL  READING-COURSES 

glass  at  table;  yet  at  school,  and  in  other  public  places,  promiscuous 
drinking  from  a  cup  is  still  too  common,  although  railroads  are  fast  abolish- 
ing the  common  cup.  Laws  have  been  passed  in  some  States  forbidding 
its  use  in  public  places. 

Railroad  dust. —  The  railway  porter's  income  is  derived  partly  from  fees 
for  brushing  the  clothes  of  passengers.  The  dust  from  the  clothing  of  one 
passenger  is  stirred  up  and  settles  on  the  plush  seats  of  the  car  and  on  the 
clothing  and  persons  of  his  fellow-passengers.  Dust  and  money  are  thus 
put  into  circulation!  Considering  the  danger  from  germ-laden  dust,  it 
is  possible  that  the  back  platform  might  be  less  dangerous  than  the  car 
aisle  as  a  place  for  the  brushing.  A  better  way  still  is  for  every  passenger 
to  do  his  own  brushing,  in  private,  on  his  own  back  doorstep. 

Food  exposed  to  dust. —  It  may  be  difficult  to  cover  all  the  left-overs 
and  all  the  food  in  process  of  preparation;  but  the  housekeeper  is  likely 
to  attempt  to  do  this  when  she  realizes  that  the  surfaces  of  uncovered 
food  catch  many  flying  particles  and  germs  that  we  would  rather  not 
have  made  a  part  of  our  diet.  Probably,  if  the  bread  had  not  been  left 
unprotected,  the  mouse  would  not  have  jumped  into  it.  We  can  see  the 
mouse,  however,  in  time  to  avoid  making  him  a  part  of  our  meal,  whereas 
the  obnoxious  germ  is  so  small  as  to  escape  notice.  v  A  table  filled  with 
left-overs,  waiting  to  be  prepared  for  the  next  meal,  is  a  veritable  dust- 
garden,  and  who  knows  what  additions  it  may  make  to  our  diet?  Of 
course,  sufficient  heat  applied  may  kill  anything  dangerous,  but  we  do 
not  want  dirt  in  our  food  even  though  the  germs  have  been  killed. 

Food  exposed  in  the  market. —  Housekeepers  are  promoting  the  interests 
of  health  when  they  buy  only  those  foodstuffs  that  are  protected,  on 
wagons  and  in  the  market,  from  the  dust  of  the  street.  Handling  foods 
with  clean  hands  necessitates  in  the  grocery  a  place  in  which  the  hands 
can  be  washed  frequently. 

Washing  clothes  without  boiling. —  There  are  pieces  in  the  laundry  that 
should  be  boiled;  handkerchiefs,  bed  linen,  underclothing,  and,  in  fact, 
all  clcthing  are  the  better  for  sterilization.  The  newer  methods  of  clean- 
ing and  pressing  woolen  suits  are  good  from  a  sanitary  standpoint.  Clean- 
ing processes  involve  steam,  which  is  a  sterilizer,  and  often  gasoline,  which 
is  a  partial  disinfectant. 

Tainted  money. —  No  one  refuses  even  a  grimy,  dirty  bank-bill,  "but 
every  one  feels  the  need  of  washing  the  hands  after  handling  it.  Placing 
coins  in  the  teeth  shows  decided  lack  of  intelligence  or  reckless  disregard 
cf  sanitary  principles.  The  coins  that  pass  through  many  hands  may 
have  become  infected  with  the  micro-organisms  of  diphtheria,  tuber- 
culosis, or  other  specific  diseases. 


HOUSEHOLD  BACTERIOLOGY  67 

Care  of  toilets. —  Public  and  private  toilets  should  be  disinfected  very 
frequently.  The  basin,  bath,  and  the  seat  especially,  need  careful  washing 
with  a  disinfecting  solution.  Cloths  and  brushes  used  about  the  toilet 
should  be  scalded  and  not  used  for  other  purposes  of  cleaning.  * 

Careless  dishwashing. —  The  thorough  washing  of  pans,  kettles,  and  cans 
makes  housework  and  cooking  far  from  easy,  but  in  the  long  run  it  is 
easier  than  caring  for  sickness  or  being  disabled.  It  is  not  so  difficult  to  do 
the  cooking  when  some  one  else  does  the  cleaning  up.  The  fewer  the 
creases  in  a  cooking  utensil  and  the  more  it  is  scalded,  the  better.  Sun 
and  hot  water  are  most  beneficial  agents  for  the  safe  care  of  kitchen 
utensils. 

The  refrigerator. —  The  refrigerator  might  be  called  or>  to  tell  many 
tales  of  the  life  history  of  germs,  for  its  recesses  hide  a  multitude  of  secrets. 
Slime  left  where  the  ice  has  melted  shows  the  need  of  care  in  cleaning  the 
refrigerator,  for  here  is  food  for  bacterial  life.  The  spilling  of  food  on 
the  shelves  is  another  source  of  the  same  trouble.  Ice  should  be  well 
washed  before  being  placed  in  the  refrigerator.  All  bits  of  food  should 
be  removed  from  the  shelves  and  crevices,  the  refrigerator  should  be 
often  washed  and  scalded,  and  some  antiseptic,  such  as  washing-soda, 
should  be  used.  The  chill  of  the  refrigerator  retards  the  growth  of 
micro-organisms,  but  probably  does  not  destroy  them. 

BACTERIA   AND   MILK 

As  milk  is  one  of  the  most  important  foodstuffs,  especially  for  children, 
it  is  very  important  that  every  housewife  should  understand  something  of 
the  effect  of  bacteria  on  it.  Every  one  knows  that  milk  contains  a  certain 
number  of  bacteria.  Some  of  the  germs  are  in  the  udder  itself,  but  most 
of  them  get  into  milk  after  it  is  drawn.  Dirty  cows,  dirty  barns  and 
stables,  dirty  hands  and  clothes  of  the  milker,  and  dirty  utensils  all  con- 
tribute to  increase  the  number  of  germs  in  milk.  If  the  milk  is  not  properly 
cooled  and  kept  cold,  bacteria  multiply  and  produce  many  changes  in 
it  which  often  trouble  nurse  and  cook. 

The  most  common  of  the  difficulties  encountered  in  caring  for  milk  is 
the  simple  souring,  or  lactic-acid  fermentation.  In  addition  to  this  well- 
known  process,  there  are  a  number  of  other  and  more  troublesome 
changes,  such  as  the  appearing  of  bitter  milk,  slimy  milk,  and  tainted 
milk. 

The  lactic  fermentation,  or  common  "  souring,"  of  milk  is  brought 
about  by  a  number  of  species  of  bacteria.  Formerly  it  was  supposed 
thai  a  single  species  produced  this  change,  which  consists  in  the  splitting 
of  the  milk-sugar  molecule  into  carbon  dioxid  and  lactic  acid.  It  is 

*  A  lesson  on  disinfection  is  in  preparation. 


68  THE  CORNELL  READING-COURSES 

now  known,  however,  that  in  the  process  of  splitting  up  the  milk-sugar 
other  by-products  are  produced.  In  the  simple  lactic  type  of  fermentation 
these  secondary  products  are  not  very  important.  It  should  be  noted, 
however,  that  in  the  souring  of  milk  by  different  species  of  bacteria, 
correspondingly  different  by-products  may  result.  In  consequence  of 
this  the  souring  is  often  accompanied  with  by-products  that  are  undesirable, 
if  not  injurious,  to  the  consumer.  In  such  cases  the  deleterious  substances 
are  often  produced  before  the  quantity  of  acid  is  sufficient  to  cause  curd- 
ling. In  fact,  the  by-products  themselves  may  become  harmful  while 
the  milk  is  still  considered  sweet  and  wholesome.  The  most  telling  truth 
that  comes  to  us  from  all  inquiries  on  the  subject  is,  that  different  bacteria 
causing  souring  in  milk  produce  very  different  effects  on  the  milk  itself, 
as  is  shown  in  the  rapidity  of  the  souring  and  in  the  types  of  fermentation 
accompanying  it. 

Much  has  been  written  concerning  disease-producing  bacteria  in  milk. 
They  belong  to  two  distinct  classes,  namely:  (i)  The  specific  bacteria 
of  certain  diseases  of  cattle,  which  may,  if  the  animal  is  suffering  from 
disease,  gain  entrance  to  the  milk.  In  this  class  may  be  mentioned 
tuberculosis,  foot-and-mouth  disease,  and  possibly  anthrax.  (2)  The 
bacteria  of  certain  human  diseases,  such  as  typhoid  fever  and  diphtheria, 
and  the  virus  of  scarlatina  and  measles.  A  large  number  of  epidemics 
of  these  diseases  has  been  traced  to  the  milk  supply;  through  it  the  infec- 
tions occurred.  The  explanation  of  this  is,  that  in  cases  in  which  the 
diseases  existed  among  the  attendants  or  in  their  homes,  sufficient  care 
was  not  taken  in  handling  milk  to  prevent  the  entrance  of  the  disease 
germs.  In  the  case  of  typhoid  fever  the  water  used  in  rinsing  utensils 
may  be  contaminated.  In  cases  of  "diphtheria  it  often  happens  that  those 
who  have  recently  apparently  recovered  from  the  disease  but  still  have 
the  bacilli  in  their  throats,  are  engaged  in  milking  or  in  otherwise  handling 
the  milk,  when,  by  sneezing  or  coughing,  the  bacilli  from  the  throat  may 
be  introduced  into  the  milk.  The  sad  experiences  of  the  past  are  teaching 
the  importance  of  taking  reasonable  precautions  against  such  infection. 

When  digestive  disorders,  especially  among  children,  follow  the  use 
of  milk  containing  many  bacteria,  the  immediate  cause  is  quite  as  likely  to 
be  the  acids  and  other  by-products  that  have  been  produced  in  the  milk 
by  various  forms  of  bacteria,  as  the  activities  within  the  digestive  tract 
of  any  one  or  more  species  of  the  micro-organisms  consumed.  We  must 
look  to  the  effect  of  bacteria  on  the  milk  itself  for  the  cause  of  many, 
but  not  all,  of  such  ailments.  It  is  to  prevent  those  effects  that  pasteur- 
ization is  employed. 

Milk  is  sterilized  or  pasteurized  for  two  purposes:  to  keep  it  sweet  for 
a  longer  time  than  would  otherwise  be  possible,  and  to  kill  all  harmful 


HOUSEHOLD  BACTERIOLOGY  69 

bacteria  that  it  may  contain.  Sterilizing  milk  means  boiling  it  for  a 
certain  length  of  time,  or  heating  it  nearly  to  the  boiling  point,  allowing  it 
to  stand  for  some  hours  and  agair  heating,  repeating  the  operation  several 
times.  Boiled  milk  is  very  difficult  for  children  to  digest.  Pasteurization 
is  accomplished  by  bringing  milk  to  a  temperature  of  60°  to  65°  C.  (140° 
to  i49°F.)  and  holding  it  there  for  twenty  minutes,  after  which  it  is  cooled 
quickly.  This  process  does  not  affect  the  taste  of  the  milk,  and  such  milk 
is  more  readily  digested  than  is  boiled  milk.  We  should  not  need  to 
depend  on  sterilizing  or  pasteurizing  as  a  means  for  providing  germ-free 
milk.  The  milk  should  be  produced  in  a  clean  manner,  for  clean  raw  milk 
is  more  wholesome  for  children  than  cooked  milk,  no  matter  what  the 
method  of  cooking  may  be.  Hot  air  and  steam  are  valued  germicidal 
agents;  hence  their  wise  use  in  the  dairy. 

The  cow  not  only  needs  wholesome  food,  but  also  needs  to  be  kept  clean. 
From  the  time  the  milk  leaves  the  udder  there  is  danger  of  its  contamina- 
tion. 

Look  first  on  this  picture :  A  milkman  dressed  in  clothes  brushed  clean, 
his  hands  washed  in  soap  and  water,  not  simply  rinsed  at  the  trough, 
his  finger  nails  short  and  clean;  the  cow  curried,  her  udder  washed;  the 
pail  to  be  used  covered  until  needed  for  the  milk;  the  stable  clear  of  dirt. 
Look  next  on  this  picture:  The  cow  lying  in  her  own  dirt  overnight,  her 
udder  soiled;  the  milkman  dressed  as  he  has  been  while  doing  all  sorts  of 
work;  the  cow's  tail  switching  and  dirt  flying;  flies  bothering  the  cow 
until  she  kicks  —  if  not  into  the  pail  it  is  only  careful  management  that 
has  prevented  such  an  occurrence.  Milk  produced  in  the  latter  way  is 
hardly  worth  buying;  while  for  that  bought  from  the  former  milkman  we 
can  afford  to  pay  a  good  price  —  enough  to  encourage  a  man  to  keep 
clean  and  to  have  clean  stables  and  cows.  Pay  enough  to  allow  the 
farmer  to  have  cement  floors,  tight  ceilings,  good  ventilating  devices, 
and  general  cleanliness.  Then  he  will  scrub  his  floors  and  will  hang  up 
his  milking  suit,  to  be  used  only  while  milking. 

"  We  always  strain  our  milk,  and  dirt  and  hairs  are  removed  from  it," 
say  some.  Yes,  but  we  do  not  like  to  eat  bread  that  the  mouse  ran  over, 
even  if  the  mouse  has  gone.  A  good  part  of  the  dirt  that  may  get  into 
milk  is  soluble  and  cannot  be  strained  out.  A  diseased  cow!  We 
think  it  not  profitable  to  throw  away  milk,  but  consider  the  danger  to 
human  beings  of  infection  from  the  use  of  impure  milk!  It  is  safe  to 
watch  the  cow,  so  as  not  to  use  the  milk  from  a  ccw  that  is  diseased. 

The  milk  that  a  certain  housekeeper  was  buying  appeared  at  one  time 
to  be  not  quite  right,  and  she  interviewed  her  milkman.  "  Many  hairs 
and  much  dirt  in  the  milk,"  was  her  complaint.  "  Oh  well,"  he  said, 
"  I  have  to  hire  my  milking  done  and  you  know  how  it  is,  they  won't 


70  THE  CORNELL  READING-COURSES 

always  be  careful;  I  have  told  the  man  if  the  cow  stepped  into  the  pail 
to  throw  the  milk  away,  but  he  won't  always  do  it  unless  he  is  watched." 

Tests  were  made  some  years  ago  by  R.  A.  Pearson,  at  that  time 
Professor  of  Dairy  Industry  at  the  New  York  State  College  of  Agricul- 
ture, and  by  Walter  E.  King  of  the  State  Veterinary  College,  in  order 
to  determine  the  importance  of  different  sources  of  milk  contamination. 
Mr.  Pearson  has  given  the  following  as  a  result  of  these  experiments : 

"  In  most  of  these  tests,  a  definite  quantity  of  sterilized  milk  at  98°  F. 
was  exposed  to  some  one  kind  of  contamination  that  we  wished  to  test. 
The  milk  was  then  examined  and  in  that  way  we  could  get  a  fairly  accurate 
idea  of  what  this  particular  kind  of  contamination  amounted  to.  Some 
of  the  experiments  and  their  results  are  as  follows: 

1.  "  Exposure  to  air  in  the  stable. —  Two  liters  (about  two  quarts)  of 
sterilized  milk  were  placed  in  a  sterile  pail  and  exposed  seven  minutes  to 
the  stable  air  in  a  passageway  behind  the  cows.     This  stable  was  doubt- 
less cleaner  than  the  average  and  the  air  contained  less  dust  than  is 
often  found  in  places  where  milk  is  being  handled.     Immediately  after 
this  exposure,  the  milk  was  '  plated  '  and.  found  to  contain  2,800  bacteria 
per   cubic   centimeter    (about   fifteen   drops);   in  other  words,   between 
5,000,000  and  6,000,000  bacteria  had  fallen  into  the  two  liters  of  milk 
in  this  short  time. 

2.  "  Pouring  milk. —  When  milk  is  poured  from  one  vessel  to  another, 
a  very  large  surface  is  exposed  to  the  air  and  great  numbers  of  bacteria 
are   swallowed    up.     The   following   tests  illustrate   this   point:     About 
five  liters  of  milk  were  poured  from  one  can  to  another  eight  times  in  the 
stable  air.     It  was  found,  after  pouring,  that  this  milk  contained  practically 
100  bacteria  per  cubic  centimeter  more  than  it  contained  before  pouring; 
in  other  words,  about  600,000  bacteria  had  got  into  the  milk  because  of 
this  exposure.     In  another  similar  experiment,  when  there  was  a  little 
more  dust  in  the  air,  the  contamination  due  to  pouring  eight  times  was 
two  and  one  half  times  greater  than  in  the  preceding  experiment. 

"  The  importance  of  pouring  milk  as  little  as  possible  from  one  vessel 
to  another  has  suggested  to  Dr.  J.  Roby,  of  the  Rochester  Health  Depart- 
ment, that  milking-pails  should  be  made  larger  than  those  now  used  and 
immediately  closed  after  the  cow  has  been  milked.  The  milk  should 
then  be  cooled  and  delivered  in  these  same  pails  without  further  exposure. 
In  some  ways  this  suggestion  is  a  most  excellent  one,  but  it  may  be  that 
under  certain  conditions  the  disadvantages  of  this  method  of  handling 
milk  would  exceed  the  advantages. 

3.  "  Contaminated  utensils. —  Much  contamination  of  milk  results  from 
putting  it  into  dishes  that  have  been  cleaned  and  then  exposed  where 
dust  can  fall  into  them.     In  experiments  to  determine  what  this  kind  of 


HOUSEHOLD  BACTERIOLOGY  71 

contamination  amounts  to,  it  has  been  found  that  when  little  care  is 
taken  to  protect  the  dishes,  the  milk  will  often  contain  several  hundred 
times  as  many  bacteria  as  when  the  utensils  were  protected  from  dust. 
In  order  to  illustrate  this  point,  two  pails  were  carefully  washed  and 
sterilized.  One  of  them  was  covered  with  sterile  cloth  to  keep  dust 
from  falling  into  it.  The  other  was  left  exposed  to  the  air  of  a  clean 
creamery  for  only  a  few  minutes.  A  small  quantity  of  sterile  milk  was 
then  put  into  each  pail,  rinsed  around,  and  then  examined  for  numbers 
of  bacteria.  It  was  found  that  the  milk  in  the  pail  which  was  not  pro- 
tected from  dust  contained  1,600  more  bacteria  per  cubic  centimeter 
than  the  milk  in  the  protected  pail. 

4.  "  Contamination  from  the  cow's  udder  and  body, —  Great  numbers  of 
bacteria  fall  into  the  milk  when  it  is  being  drawn  from  the  udder,  because 
the  milking  pail  is  directly  under  the  udder  which  is  being  shaken  more 
or  less   by   the  milker's  hands.     This  kind   of  contamination  may  be 
reduced  by  cleaning  the  udder.     It  was  found  that  sterile  milk  exposed 
under  the  udder  as  long  as  it  takes  to  milk  a  cow,  and  while  the  udder 
was  being  shaken  about  the  same  as  when  milk  is  being  drawn,  con^ 
tained  19,000  bacteria  per  cubic  centimeter.     In  this  case  the  udder  had 
been  wiped  off  with  a  dry  cloth  much  in  the  same  way  as  is  done  in  fairly 
good  dairies. 

"  In  a  similar  test,  the  udder  was  wiped  with  a  damp  cloth  and  then 
the  number  of  bacteria  was  reduced  to  4,500  per  cubic  centimeter.  In 
a  third  experiment  the  udder  was  wiped  with  a  cloth  dampened  in  a 
4-per-cent  carbolic  acid  solution;  then  the  number  of  bacteria  was  3,200 
per  cubic  centimeter.  In  cases  in  which  no  particular  care  is  taken  to 
clean  the  udder,  the  bacteria  getting  into  the  milk  from  this  source  may 
run  up  into  the  hundreds  of  thousands  or  millions. 

5.  "Importance  of  small  openings  in  milk  pails. —  Thus  it  is  seen  that 
it  is  impracticable  to  clean  the  udder  or  free  the  air  from  dust  so  perfectly 
that  rfo  bacteria  will  fall  into  the  milk.     The  next  question  is,  how  can 
we  reduce  the  number  of  those  that  will  fall  in  spite  of  all  reasonable 
precautions?     The  easiest  way  known  is  to  use  a  small-top  milking- 
pail.     Reduce   the    opening   through  which  dirt  can  fall  into  the  pail. 
An  experiment  was  conducted  to  illustrate  this  point,  and  it  was  found 
that  milk  drawn  in  an  ordinary  milking-pail  contained  1,300  bacteria 
per  cubic  centimeter,   while  that  drawn  in  a  pail  with  opening  about 
one  half  as  wide  contained  only  320  bacteria  per  cubic  centimeter.     This 
is  just  what  we  would  expect  when  we  compute  the  number  of  square 
inches  through  which  dust  can  fall  into  the  different  kinds  of  pails.     For 
example,  a  pail  having  a  top  14  inches  in  diameter  has  an  opening  of  153.86 


THE  CORNELL  READING-COURSES 


square  inches;  a  pail  with  1 2-inch  top  has  an  opening  of  113.04  sqi 
inches;  one  with  lo-inch  top  has  an  opening  of  79.79  square  inches;  a 

with  an  opening  of  6  inc 
in  diameter  has  an  exj 
of  28.26  square  inches. 

"  Milkers   should    get 
the  habit  of  using  the 
top  pail,  as  it   is  one 

FIG.  29  —  Diagram  showing  size  of  openings  in       easiest  of  all  ways  for 
various  kinds  of  milk  pails.      The  large  circle 

at  the  left  represents  the  common  milk  pail.        mg    the    number    OI    bad 
The  others  show  the  perpendicular  exposure  in       that  fall  into  milk. 
the  new  kinds  of  pails 

6.     Contamination  by  flie. 

A  fly  or  a  bit  of  hay  or  straw  or  a  piece  of  sawdust  or  a  small  hair, 
carry  enormous  numbers  of  bacteria  into  milk  as  is  shown  by  the  fc 
ing  experiments : 

"A  living  fly  was  introduced  into  500  cubic  centimeters  of  sterile 
The  milk  was  shaken  one  minute  and  then  it  contained  42  bacteria 
cubic  centimeter.  After  24  hours  at  room  temperature,  it  contai 
765,000  bacteria  per  cubic  centimeter,  and  after  26  hours  5,675,000. 

7.  "  Dirt  in  the  milk. —  A  piece  of  hay  about  two  inches  long  was  pla| 
in  500  cubic  centimeters  of  sterile  milk.     The  milk  was  shaken  one  mi 
and  it  then  contained  3,025  bacteria  per  cubic  centimeter.     After  24  h 
at  room  temperature  it  contained  3,412,500  bacteria  per  cubic  centime 

"  One  piece  of  sawdust  from  the  stable  floor  was  put  into  500 
centimeters  of  sterile  milk.     The  milk  was  shaken  one  minute  and 
bacterial  content  was  then  found  to  be  4,080  per  cubic  centimeter. 
24  hours  at  room  temperature  it  was  7,000,000  per  cubic  centimeter. 

"A  hair  from  a  cow's  flank  was  put  into  500  cubic  centimeters  of  s 
milk.  After  shaking  the  milk  for  one  minute  it  contained  52  bacteria 
cubic  centimeter.  After  24  hours  at  room  temperature  it  contained  55, 
per  cubic  centimeter,  and  after  36  hours  over  5,000,000  bacteria  per 
centimeter." 

REFERENCES    FOR   FURTHER   STUDY 

Belcher,  S.  D.     Clean  milk.     Hardy  Publishing  Company,  New  Yor 

Conn,  H.  W.     Agricultural  bacteriology.     P.  Blakiston's  Son  &  Co. 
The  story  of  germ  life.    D.  Appleton  &  Co.,  New  Y 
Bacteria,  yeasts,  and  molds  in  the  home.      Ginn  & 
Practical  dairy  bacteriology.     Orange  Judd  Com 
New  York 

Elliott.     Household  bacteriology.     American  School  of  Home  Econ< 
Chicago 

Lipman.    Bacteria  in  relation  to  country  life.    The  Macmillan  Compa] 

Marshall.     Microbiology.     P.  Blakiston's  Son  &  Co. 


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